Integrated complex nano probe card and method of making same

ABSTRACT

An integrated complex nano probe card is disclosed to include a substrate layer having a front side and a back side, and complex probe pins arranged in the substrate layer. Each complex probe pin has a bundle of aligned parallel nanotubes/nanorods and a bonding material bonded to the bundle of aligned parallel nanotubes/nanorods and filled in gaps in the nanotubes/nanorods. Each complex probe pin has a base end exposed on the back side of the substrate layer and a distal end spaced above the front side of the substrate layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a probe card for testingelectronic elements and its fabrication method and, more specifically,to an integrated complex nano probe card. The invention relates also tothe fabrication of the integrated complex nano probe card.

2. Description of the Related Art

A variety of probe cards for testing electrical properties of anelectronic element are commercially available. These probe cards includetwo types, i.e., the cantilever type and the vertical type. The probepins of these two types of probe cards are tungsten pins, lead pins, orberyllium copper pins manually installed in a printed circuit board. Thepitch of the probe pins of a cantilever type probe card is about 50 μm.The pitch of the probe pins of a vertical type probe card is about 100μm. Due to technical limitations, the pitch of the probe pins of eithertype of probe cards cannot be reduced as desired to fit measuringrequirements for nanoelectronics. Further, because probe pins areinstalled in a printed circuit board manually, the manufacturing cost isrelatively increased with the increasing of pin counts. This drawbackcauses the aforesaid conventional probe cards unable to meet futuredemand.

U.S. Pat. No. 6,232,706 discloses a field emission device having bundlesof aligned parallel carbon nanotubes on a substrate. The carbonnanotubes are oriented perpendicular to the substrate. The bundles ofcarbon nanotubes extend only from regions of the substrate patternedwith a catalyst material. The substrate is porous silicon. Thefabrication of the field emission device starts with forming a porouslayer on a silicon substrate by electrochemical etching. Then, a thinlayer of iron is deposited on the porous layer in patterned regions. Theiron is then oxidized into iron oxide, and then the substrate is exposedto ethylene gas at elevated temperature. The iron oxide catalyzes theformation of bundles of aligned parallel carbon nanotubes, which growperpendicular to the substrate surface.

The advantages of U.S. Pat. No. 6,232,706 include (1) small nanotubepitch, and (2) manufacturing cost of nanotubes being not determinedsubject to the pin counts. However, this design still has drawbacks.Because nanotubes are not linked to one another, the whole structure isbulky, resulting in low physical and electrical properties of nanotubes.Further, due to low impact strength of carbon material, nanotubes tendto be broken when pressed by an external object. Due to the aforesaiddrawbacks, nanotubes made according to U.S. Pat. No. 6,232,706 are notsuitable for use as probe pins in a probe card.

Further, U.S. Pat. No. 5,903,161 discloses an electrically conductiverod-shaped single crystal product, which is a rod-shaped single crystalformed by a vapor-liquid-solid method or such a rod-shaped singlecrystal having its forward end alloy portion removed, and the surface ofthe rod-shaped single crystal is coated by an electrically conductivefilm. However, this rod-shaped single crystal product has a low electricconductivity due to its limited electric conducting area.

SUMMARY OF THE INVENTION

The present invention has been accomplished under the circumstances inview. It is therefore the main object of the present invention toprovide a complex probe pin, which has good physical properties as wellas good electrical properties. To achieve this object, the complex probepin comprises a bundle of aligned parallel nanotubes/nanorods, and abonding material bonded to the bundle of aligned parallelnanotubes/nanorods and filled in gaps in the nanotubes/nanorods.

It is another object of the present invention to provide a probe cardhaving integrated complex nano probe pins, which has a small probe pinpitch and is inexpensive to manufacture. To achieve this object, theprobe card comprises a substrate layer having a front side and a backside, and complex probe pins arranged in the substrate layer. Eachcomplex probe pin is comprised of a bundle of aligned parallelnanotubes/nanorods, and a bonding material bonded to the bundle ofaligned parallel nanotubes/nanorods and filled in gaps in thenanotubes/nanorods. Each complex probe pin has a base end exposed to theoutside of the back side of the substrate layer, and a distal end spacedabove the front side of the substrate layer.

It is still another object of the present invention to provide a probecard fabrication method, which minimizes the pitch of probe pins,improves the physical and electrical properties of probe pins, andincreases pin accounts without increasing much manufacturing cost. Toachieve this object, the probe card fabrication method comprises thesteps of (1) preparing a substrate having a porous surface; (2) coveringa catalyst material on the porous surface of the substrate subject to apredetermined pattern, so as to form a plurality of catalyst strips onthe porous surface of the substrate, the catalyst strips each comprisinga plurality of catalyst elements; (3) exposing the catalyst strips to anenvironment containing a predetermined gas and having a temperatureabove room temperature, for enabling the catalyst elements to react withthe gas so as to form bundles of aligned parallel nanotubes/nanorods atthe catalyst strips; and (4) covering the bundles of aligned parallelnanotubes/nanorods by a bonding material, enabling the bonding materialto pass into gaps in the aligned parallel nanotubes/nanorods.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a finished product obtained after step (1)of the probe card fabrication method according to the present invention.

FIG. 2 is a top view of a finished product obtained after step (2) ofthe probe card fabrication method according to the present invention.

FIG. 3 is a sectional view of a finished product obtained after step (3)of the probe card fabrication method according to the present invention.

FIG. 4 is a sectional view of a finished product obtained after step (4)of the probe card fabrication method according to the present invention.

FIG. 5 is an enlarged view of part A of FIG. 4.

FIG. 6 is a sectional view taken along line 6-6 of FIG. 5.

FIG. 7 is a sectional view of a finished product obtained after step (5)of the probe card fabrication method according to the present invention.

FIG. 8 is a sectional view of a finished product obtained after step (6)of the probe card fabrication method according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1˜4, a probe card fabrication method includes thesteps of:

(1) Prepare a p-doped n+-type si(100) substrate 10, then usehydrofluoric acid solution and platinum served as a cathode toelectrochemically etch one surface 11 of the substrate 10, forming pores12 in the surface 11, each pore 12 having a diameter below 3 nm, asshown in FIG. 1.

(2) Use lithography and evaporation techniques to cover a catalystmaterial, for example, iron (Fe), on the surface 11, forming a matrix ofcatalyst strips 20 on the surface 11, each catalyst strips 20 havingdensely arranged fine catalyst elements 21, as shown in FIG. 2.

(3) Put the substrate 10 in a CVD (chemical vapor deposition) stovepipe, then increase the temperature in the stove pipe properly andsupply a carbon-contained gas, for example, C₂H₂, causing the catalystelements 21 to make a chemical reaction with the supplied gas, so thatbundles 30 of aligned parallel carbon nanotubes 31 are crystallized andrespectively formed in the catalyst strips 20 and extended in directionsubstantially perpendicular to the surface 11 of the substrate 10, asshown in FIG. 3.

(4) Cover the bundles 30 by a bonding material, for enabling the appliedbonding material to pass into gaps in carbon nanotubes 31. According tothis embodiment, a metal material of good electrical properties andmechanical properties, for example, copper 40 is covered on the bundles30 by electroplating, enabling copper 40 to pass into gaps in carbonnanotubes 31 of each bundle 30, forming complex probe pins 50 on thesubstrate 10, as shown in FIG. 4.

With reference to FIGS. 5 and 6, the compound probe pin 50 made subjectto the aforesaid method comprises a bundle 30 of substantially alignedparallel carbon nanotubes 31 and a metal material 40 covered on thebundle 30 (see FIG. 5) and filled up the gaps in the carbon nanotubes 31(see FIG. 6). Because the bundle 30 is covered by the metal material 40and the carbon nanotubes 31 are fixedly fastened to one another by themetal material 40, the compound probe pin 50 has a dense structure, andgood mechanical, physical and electrical properties. Rubber may be usedas the bonding material.

After the aforesaid four steps, each complex probe pin 50 has a base endand a distal end. The base end is fixedly connected to the surface 11 ofthe substrate 10 by one catalyst strip 20.

With reference to FIGS. 7 and 8, after the aforesaid four steps, itproceeds to the following steps:

(5) Apply a layer of liquid epoxy resin to the surface 11 of thesubstrate 10, enabling the layer of liquid epoxy resin to cover the baseends of the complex probe pins 50 and to form a substrate layer 60 whenhardened as shown in FIG. 7.

(6) Remove the substrate 10 from the substrate layer 60. At this time,the substrate layer 60 has a front side 61 and a back side 62, the baseends of the complex nano probe pins 50 are exposed out of the back side62 of the substrate layer 60, and the distal ends of the complex nanoprobe pins 50 are spaced above the front side 61 of the substrate layer60. A metal conducting block 70 is then respectively formed in theexposed base end of each complex nano probe pin 50 for connection eitherdirectly or indirectly to a printed circuit board, forming a probe card.

As indicated above, the invention uses nanotechnology to form multiplecomplex probe pins at a time, so that the pitch of probe pins can begreatly reduced. A probe card made according to the present invention issuitable for measuring electrical properties of nanoelectronic elements.Because multiple complex probe pins are formed at a time, it breaks thelimitation that the manufacturing cost is directly proportional to pincounts, and the manufacturing cost is greatly lowered. Because complexprobe pins made according to the present invention have a goodstructure, they provide good mechanical, physical and electricalproperties.

In the aforesaid fabrication procedure, iron (Fe) and C₂H₂ arerespectively used in step (2) and step (3). Other suitable metalmaterials and gases may be used. For example, when gold (Au) is used asa catalyst material, SiCl₄+H₂ is supplied to the stove pipe, causingformation of bundles of aligned parallel silicon nanorods, which growperpendicular to the substrate surface.

Further, arc-discharge or laser evaporation may be used to substitutefor chemical vapor deposition.

The material for bonding nanotubes/nanorods can be selected from gold,nickel, nickel alloy, silver, tungsten alloy, copper, or beryllium.Because carbon nanotubes have good electric conductivity, insulatingmaterial, for example, rubber may be used and covered on the peripheryof each bundle of carbon nanotubes, leaving the top end of each bundleof carbon nanotubes exposed to the outside for electric connection.

Although a particular embodiment of the invention has been described indetail for purposes of illustration, various modifications andenhancements may be made without departing from the spirit and scope ofthe invention. Accordingly, the invention is not to be limited except asby the appended claims.

1. A complex nano probe pin comprising a bundle of aligned parallelnanotubes/nanorods grown from a patterned catalyst strip on a planarsubstrate, and a bonding material bonded to said bundle of alignedparallel nanotubes/nanorods and filled in gaps between saidnanotubes/nanorods; wherein said planar substrate has a porous surface;and wherein said bonding material covers said bundle of aligned parallelnanotubes/nanorods and fills up gaps in between said nanotubes/nanorods.2. The complex nano probe pin as claimed in claim 1, wherein thenanotubes/nanorods of said bundle of aligned parallel nanotubes/nanorodsare formed of carbon.
 3. The complex nano probe pin as claimed in claim1, wherein said bonding material is copper.
 4. The complex nano probepin as claimed in claim 1, wherein said bonding material is rubber. 5.The complex nano probe pin as claimed in claim 1, wherein said bondingmaterial covers the periphery of said bundle of aligned parallelnanotubes/nanorods and fills up gaps in between said nanotubes/nanorods.